DYNAMICS OF LASER-ABLATION TRANSFER THERMAL IMAGING - FUNDAMENTAL MECHANISMS INVESTIGATED BY SIMS SURFACE-ANALYSIS

We have studied the dynamics of laser ablation transfer thermal imaging through an examination of residual and receptor surfaces following ablative transfer, utilizing secondary ion mass spectrometry to probe the surface structure and composition of the ablated material. We have elucidated the fundamental mechanisms that differentiate the ablation dynamics with and without a dynamic release layer (DRL). The region of incipient degradation is determined by the particular combination of laser and material parameters; above a certain power density threshold, the function of the DRL is revealed by the presence of an aluminum peak in the residual spectrum, indicating that localized decomposition occurs in the immediate vicinity of the ultrathin metal layer. Type II films, incorporating the DRL, may also ablate, however, according to the Type I explosive mechanism, whereby partial polymer decomposition instantly occurs throughout a sizable interior section of the coating. In the absence of the DRL, ablation is strictly initiated by an explosive transfer of superheated polymer fragments. Whereas Type II ablation may always appear to be maintained from a macroscopic perspective, on a molecular level the dynamics may actually embody some of the explosive characteristics of the Type I mechanism.